Leonard Nimoy's Spock beams onto 'Big Bang Theory'

Actor Leonard Nimoy attends the premiere of the movie "Star Trek" at the Grauman's Chinese theatre in Hollywood, California in this April 30, 2009 file photograph. Nimoy will appear in a recurring role in the FOX television series "Fringe." REUTERS/Mario Anzuoni/Files (UNITED STATES ENTERTAINMENT HEADSHOT)

"For years, we thought it would be fantastic to have Leonard Nimoy appear on the show and we think we’ve found a really different and fun way to make that happen," executive producer Steve Molaro tells THR. "As thrilled as we are he's doing it, we're even more thrilled just to get our pictures taken with him.”

Nimoy has been at the top of the producers' wish list for guest stars, as Sheldon's obsession with "Star Trek" has been well documented on the series.

Co-creator Chuck Lorre told THR at "Big Bang's" 100th episode party last year that the episode in which Penny (Kaley Cuoco) gives Sheldon a Nimoy-signed napkin -- complete with his DNA -- stands as his favorite "nerd moment" on the long-running series.

“[Sheldon] was so overcome with affection for her, he physically hugged her, which he can’t do as a character," he said at the time. "We all stood there on the stage and everybody got all fablungent and weepy. It was a moment that rose above the show and became something else.”

Added Cuoco: "He hugs her and it’s very special. I think that’s why we haven’t done a holiday episode since because they like to show that one because it’s such a sweet moment. He hasn’t hugged me since.”

The "Big Bang" guest gig is the latest in a string of voice-over roles for Nimoy, which have included "Transformers: Dark Side of the Moon" and "Land of the Lost." He also had an on-screen cameo as Spock Prime in J.J. Abrams "Star Trek" feature in 2009.